1. Field of the Invention
The invention relates to an automotive lighting system, and more particularly to an LED optical assembly for automotive low-beam headlamps.
2. Description of the Related Art
High power white LEDs have developed so rapidly over recent years that effective and energy-conscious LED illumination technology becomes more and more mature. Many industrial players initiated their research in respect of application concerning high power white LEDs in automotive lamps and sophisticated products have also been released. LED automotive lamps are not only energy-efficient but also diverse and stylish in terms of outer appearance. Headlamps must be safe while illuminating the road ahead. Many countries impose harsh restrictions upon low-beam headlamps that are required to have clear cut-off lines so as to prevent drivers from being glazed by the lights coming from opposite cars. As for traditional automotive headlamps, most of them adopt a simple reflector or a reflector teamed up with a light blocker and a delineascope containing a collector lens in the front to fulfill such requirement of cut-off lines. Both methods mentioned above can only use the lights that are directed to the reflector from the light source and the remaining lights must be blocked or diffused to eliminate possible hazards, which results in low utilization efficiency of lights. The light utilization efficiency of the former is 40% more or less and the latter impossible to exceed 60%. From this point of view, the optical design involving automotive low-beam headlamps is a key and tough issue for automobile headlamps. Thought some prestigious lighting facilities manufacturers have released several LED automotive headlamps for certain high-end limousines, the light utilization efficiency still has sufficient room for improvement as those products adopt traditional optical forms. Comparing with traditional light source in terms of light output, current white LEDs used for illumination are not up to the standard. Under such circumstance, more LEDs have to be used to compensate such shortcomings, thus directly causing the risk of overheat. In order to effectively disperse excessive heat, extra cost is incurred, which makes it difficult for the LED lamps to popularize. Besides what is mentioned before, if continued to use traditional optical design, the puzzle of low light utilization efficiency might come out. The traditional automotive low-beam headlamp with cut-off lines adopting LED as light source chiefly consists of a lens, a frame assembly, and LED illuminating chips. The lens has a non-rotational and non-spherical curve surface and is composed of several lenses each of which also has a non-rotational and non-spherical curve surface and faces towards different directions. Those lenses are connected with each other to from the lens. A main lens is located in the front and auxiliary lenses surround it. According to this approach, although the main lens and auxiliary lenses use all the lights emitted by the light source and a section of straight light area with cut-off lines is formed without blocking any light, the light area formed by the main lens direct toward right front and on the other hand, the lights from those auxiliary lenses direct toward different directions. Therefore, reflectors are needed to reflect those lights from the auxiliary lenses to the right front, thus increasing both volume and cost of automotive lamps. As described above, the light output of a single LED is rather limited, more than one set of light source and reflectors must be put together to meet illumination requirements. Nevertheless, it seems rather difficult for a tiny automotive lamp to hold so many optical assemblies.